Some useful (and fun) tutorial Git videos:
- Git For Ages 4 And Up
- RailsConf 2008 Git Talk by Scott Chacon screencast (original). 17 minutes in describes branching and (3-way!) merging.
- Lots of tutorial videos here: Gitcasts
And some regular web pages:
- The Git Parable
- Git on del.icio.us
- A git branching model (though can be applied to any VCS to be honest).
- Workflow and another branching model.
And then a touch of reality: